Knoop hardness test

Test for determining the hardness of a material in which calibrated machines force a rhombic-base pyramidal diamond indenter having specified edge angles into the surface of the material. After the applied load is removed, the length of the long diagonal is measured and the area of indentation is calculated. The result is expressed as the Knoop hardness number. See Brinell hardness test; Rockwell standard hardness test; Rockwell superficial hardness test; Scleroscope hardness test; Vickers hardness test.